The present invention generally relates to cooling systems for internal combustion engines. More particularly, the present invention relates to cam drive cooling arrangements for use in such engines.
Personal watercraft include internal combustion engines that are used to power marine propulsion units. The internal combustion engines are contained within substantially enclosed engine compartments. In most personal watercraft, the internal combustion engines are two-cycle engines. Two-cycle engines, however, have recently come under attack for their high hydrocarbon output. Accordingly, several techniques are being developed to reduce the emissions of such engines. Another response has been to replace the two-cycle engines with four-cycle engines. This is not without its difficulties. The four-cycle engines are more complicated to operate and control. In addition, a number of additional components are required. One of the components included in some four-cycle engines is a cam drive arrangement. The cam drive arrangement is used to operate exhaust and intake control valves, which valves are needed to control the induction of fresh air-fuel charges and the expulsion of spent exhaust gases from within the combustion chamber.
Cam shafts typically are driven through a belt drive arrangement that receives power from a pulley or sprocket mounted to the crankshaft. The power from the crankshaft is transmitted to the cam shafts through a belt or other flexible transmitter. In some applications, a gear train is used. In applications featuring a belt, a belt chamber is necessitated by the marine environment in which the watercraft are used. Salt water and other water spray encountered during operation of the watercraft, even within the substantially protected engine compartment, can cause corrosion of the belt and the other components of the cam drive arrangement.
To eliminate the problems associated with salt water and other water spray within the engine compartment, a cover arrangement has been designed to enclose the cam drive arrangement. The cam drive chamber, however, is susceptible to increased temperatures over the course of normal operation of the vehicle. The increased temperatures can damage the timing belts used in the cam drive arrangement.
Accordingly, it is desired to provide a cooling system for the cam drive arrangement. The cooling system should function to reduce or monitor or moderate the temperature within the cam drive chamber. In addition, the cooling arrangement should be integrated into a cover arrangement that is designed to protect the cam drive arrangement from the corrosive effects of the marine environment in which the watercraft is operated. By integrating the cooling system with the cover, the size and weight of the overall system can be advantageously reduced.
Accordingly, one aspect of the present invention involves an engine for a personal watercraft. The engine comprises an engine body comprising a crankcase member, a cylinder block and a cylinder head. At least one cam shaft extends outside of the engine body. A driven pulley is attached to the at least one cam shaft and is positioned outside of the engine body. A crankshaft also extends outside of the engine body. A drive pulley is connected to the crankshaft and is positioned outside of the engine body. A flexible transmitter is looped around the driven pulley and the drive pulley. A chamber is defined by at least a portion of the engine body and a first cover member. A cooling jacket extends through at least a portion of the first cover member.
Another aspect of the present invention involves an engine for a personal watercraft. The engine comprises an engine body comprising a crankcase member, a cylinder block and a cylinder head. The engine also comprises at least one cam shaft. A driven pulley is attached to the at least one cam shaft. A drive pulley is connected to the crankshaft. A flexible transmitter is looped around the driven pulley and the drive pulley. A chamber is defined by at least a portion of the engine body. A first cover member and a second cover member are provided. The engine body comprising a first sealing surface positioned on at least one of the cylinder block and the crankcase member and a second sealing surface positioned on at least one of the cylinder block and the cylinder head. A first opening is defined through the second cover member and the engine body. The crankshaft extends through the first opening. A second opening is defined through the second cover member and the engine body. The at least one cam shaft extends through the second opening. A third sealing surface is formed on the second cover member. The third sealing surface extends at least partially around the first opening and abuts at least a portion of the first sealing surface. A fourth sealing surface is formed on the second cover member. The fourth sealing surface extends at least partially around the second opening and abuts at least a portion of the second sealing surface. The first cover member abuts the second cover member and encloses at least one of the first opening and the second opening.
A further aspect of the present invention involves an engine for a personal watercraft. The engine comprises at least one drive pulley, at least one driven pulley and a flexible transmitter coupling the drive pulley and the driven pulley. The drive pulley, the driven pulley and the flexible transmitter are positioned within a belt chamber. The engine further comprises means for cooling the belt chamber.